In our on-going study, as suggested by the reviewing study section, we have concentrated on the examination of antitumor activity of the hormone-like peptide, tuftsin. Based on these results, we are now proposing to undertake the following studies to prepare for the future clinical study of this compound as a biological response modifier for cancer: 1. To produce a sufficient quantity fo highly purified tuftsin by the solid phase procedure and liquid chromatographies. 2. To develop a sensitive immunoassay to determine the levels of tuftsin. Monoclonal antibody will be produced against tuftsin-conjugated bovine serum albumins utilizing the hybridoma technique to establish an enzyme-lined immunosorbent assay for tuftsin. 3. To determine the most effective mode of administration of tuftsin. Three mouse systems, Ch1 B cell lymphoma, B-16 melanoma and Lewis lung carcinoma, will be utilized for this purpose. 4. To perform the toxicity study of the synthetic tuftsin using three species of animals, mouse, rabbit, and dog.